Analysis method of residual acid of alcohol compound

Abstract

To provide a method for accurately analyzing residual acid of an alcohol compound.SOLUTION: An analysis method of residual acid of an alcohol compound includes: providing organic solvent and inputting organic solvent into a distiller to distill the organic solvent, and obtain refined organic solvent being an intermediate part of a distillation process; mixing a basic inorganic compound with the refined organic solvent to prepare titrant; mixing a diol compound with the refined organic solvent to prepare a sample to be tested; and performing acid-base titration to the sample to be tested prepared by the prepared titrant to analyze the amount of residual acid of the diol compound. Herein, the normality of basic inorganic compound in the titrant is 0.005 N or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for analyzing a compound, and more particularly to a method for analyzing residual acids in alcohol compounds. [Background technology]

[0002] Conventionally, when a diol compound (e.g., an aromatic dihydroxy compound) serving as a reaction material undergoes a transesterification reaction, a basic inorganic compound (e.g., potassium hydroxide (KOH) or sodium hydroxide (NaOH)) is used as an auxiliary reagent to catalyze the transesterification reaction. In this case, if the amount of auxiliary reagent used is small, the catalytic effect of the auxiliary reagent is affected if the diol compound contains too much residual acid.

[0003] The specification of Patent Document 1 describes that an alkali metal hydroxide (e.g., NaOH) may be added to a reaction mixture for synthesizing polycarbonate (PC) in order to enhance the activity of the main catalyst, which is polyhydropolyborate. The amount of alkali metal hydroxide used is about 10 moles per mole of the aromatic dihydroxy compound used. -7 ~10 -5 The amount used is preferably in mgKOH / g (analysis unit of acid value), which is about 2.4 × 10 -6 ~2.4×10 -4 mgKOH / g.

[0004] However, residual acids contained in diol compounds (aromatic dihydroxy compounds) such as bisphenol A (BPA) can affect the reactivity of alkali metal hydroxides. Therefore, to prevent the residual acids in the diol compounds from affecting the reactivity of the alkali metal hydroxides (such as the co-catalyst effect), it was necessary to adjust the concentration of the residual acids contained in the diol compounds to the same level as the amount of alkali metal hydroxide used before the transesterification reaction.

[0005] The conventional standard method for acid-base titration is ASTM D664, and the lowest detectable residual acid in a material using this method is approximately 0.05 to 0.1 mg KOH / g. Therefore, residual acids below 0.05 mg KOH / g cannot be detected, making it impossible to accurately measure the residual acid in diol compounds due to the detection limit. This situation made it impossible to determine whether the residual acid in diol compounds could be controlled to the same concentration as basic inorganic compounds. Simply put, in alcohol chemical products, it was difficult to perform high-precision detection when the acid value was below 0.01 mg KOH / g or when a high-precision detection of 0.0001 mg KOH / g was required. However, residual acidic substances in alcohol chemical products affect the catalytic reactivity of subsequent chemical reactions. Therefore, the acid value of alcohol compounds needed to be measured with high precision.

[0006] Therefore, in order to solve the above-mentioned problems, the inventors have conducted extensive research and applied scientific theory, and as a result, have arrived at the present invention as a method that is rational in design and can effectively solve the above-mentioned problems. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Taiwan Patent No. I290537 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in response to the shortcomings of the prior art, and aims to provide a method for analyzing residual acids in alcohol compounds with high accuracy. [Means for solving the problem]

[0009] To solve the above technical problems, one technical solution adopted by the present invention provides a method for analyzing residual acids of alcohol compounds. The method for analyzing residual acids of alcohol compounds of the present invention includes the following steps: preparing an organic solvent, introducing the organic solvent into a distiller to distill the organic solvent, removing at least the first 10% of the distillate distilled from the distiller, and collecting the middle portion of the distillate distilled from the distiller to obtain a purified organic solvent; preparing a titration solution by mixing a basic inorganic compound with at least a portion of the purified organic solvent; preparing a test sample by mixing a diol compound to be measured with at least a portion of the remaining purified organic solvent; and titrating the test sample with the titration solution to analyze the amount of residual acids of the diol compound.

[0010] Here, the equivalent concentration of the basic inorganic compound in the titrant is 0.005N or less.

[0011] Preferably, the organic solvent is ethanol, the basic inorganic compound is potassium hydroxide, and the diol compound is an aromatic dihydroxy compound.

[0012] Preferably, in the organic solvent preparation step, at least the first 10% to 15% of the distillate distilled from the distiller is removed, then the middle 10% to 15% to 90% to 95% of the distillate distilled from the distiller is collected, and the final 5% to 10% of the distillate distilled from the distiller is removed.

[0013] Preferably, the first distillate distilled from the still contains low boiling point aldehyde compounds, and the last distillate distilled from the still contains high boiling point acid compounds.

[0014] Preferably, the step of preparing the organic solvent further includes purging the organic solvent with nitrogen gas for 10 to 30 minutes before distilling the organic solvent in the distiller, and then distilling the organic solvent in the distiller filled with the nitrogen gas.

[0015] Preferably, the equivalent concentration of the basic inorganic compound in the titrant is 0.0001N to 0.005N.

[0016] Preferably, the equivalent concentration of the basic inorganic compound in the titrant is 0.0005N to 0.005N.

[0017] Preferably, the weight ratio of the diol compound to the organic solvent in the test sample (the diol compound:the organic solvent (weight ratio) in the test sample) is 1:1 to 1:4.

[0018] Preferably, the step of preparing a test sample further comprises purging a mixture of the diol compound to be measured and at least a portion of the remainder of the purified organic solvent with nitrogen gas.

[0019] Preferably, the titration step involves acid-base titration using potentiometric titration. [Effects of the Invention]

[0020] One of the advantageous effects of the present invention is that the method for analyzing residual acids of alcohol compounds according to the present invention includes the following technical features: "a step of preparing an organic solvent, introducing the organic solvent into a distiller to distill the organic solvent, removing at least the first 10% of the distillate distilled from the distiller, and collecting the intermediate portion of the distillate distilled from the distiller to obtain a purified organic solvent," "a step of preparing a titration solution by mixing a basic inorganic compound with at least a portion of the purified organic solvent," "a step of preparing a test sample by mixing a diol compound to be measured with at least a portion of the remaining purified organic solvent," and "a titration step of performing acid-base titration on the test sample with the titration solution to analyze the amount of residual acids of the diol compound." These technical features can improve the accuracy of detecting residual acids of alcohol compounds, thereby enabling detection of residual acids of alcohol compounds at sufficiently low concentration levels and improving the detection limit. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a flowchart of a method for analyzing residual acids in alcohol compounds according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] To better understand the features and technical contents of the present invention, please refer to the following detailed description of the present invention and the accompanying drawings, which are provided for reference and explanation only and are not intended to limit the scope of the present invention.

[0023] The present invention will be described below with reference to certain specific embodiments, so that those skilled in the art can understand the advantages and effects of the present invention based on the contents disclosed herein. The present invention can also be implemented or applied in other different specific embodiments, and various modifications and changes can be made to the details in this specification based on different perspectives and applications without departing from the concept of the present invention. In addition, the accompanying drawings of the present invention are for simple schematic illustrations. The technical content of the present invention will be described in more detail below with reference to the embodiments, but the protection scope of the present invention is not limited by the contents disclosed below.

[0024] In this specification, terms such as "first," "second," and "third" may be used to describe various materials or parameters, but these materials or parameters are not limited by these terms. These terms are primarily used to distinguish one material from another or one parameter from another.

[0025] Furthermore, the term "or" as used herein may include any one or more combinations of the associated listed items, depending on the actual circumstances.

[0026] Traditionally, basic inorganic compounds (e.g., potassium hydroxide or sodium hydroxide) have been used as catalysts in transesterification reactions to synthesize polycarbonates. However, excessive residual acid in diol compounds (e.g., bisphenol A) can affect catalytic activity. Therefore, the residual acid in the diol compound (e.g., bisphenol A) must be adjusted to the same concentration as the catalyst used. The current standard method for acid-base titration (ASTM D664) cannot accurately detect residual acid concentrations below 0.05 mg KOH / g, making it impossible to determine whether the residual acid concentration in the diol compound has been properly controlled. This can affect the efficiency of the transesterification reaction and the quality of the product.

[0027] [Method for analyzing residual acids in alcohol compounds] In order to solve the above-mentioned technical problems, the present invention provides a method for analyzing residual acids of alcoholic compounds, which has a detection accuracy of residual acid analysis that can reach a concentration level of 0.0001 mg KOH / g.

[0028] 1, the method for analyzing residual acids of alcohol compounds includes steps S110, S120, S130, and S140. It should be noted that the order and operation method of each step in this embodiment can be adjusted according to needs and is not limited thereto.

[0029] In step S110, an organic solvent is provided and the organic solvent is put into a distiller to be distilled, thereby carrying out an organic solvent preparation step.

[0030] In the organic solvent preparation step, the initial distillate is removed by not collecting at least the first 10% (preferably the first 10% to 15%) of the distillate distilled from the distiller, and then an intermediate portion of the distillate distilled from the distiller (e.g., from a lower limit of 10% to 15% to an upper limit of 90% to 95%) is collected to obtain a purified organic solvent. The obtained purified organic solvent may be stored. Alternatively, in the organic solvent preparation step, the final portion of the distillate distilled from the distiller (e.g., the last 5% to 10%) may be removed rather than collected.

[0031] In one embodiment of the present invention, taking 5.0 kg of organic solvent as an example, in the preparation process of the organic solvent, the first 15% of the distillate distilled from the still is not collected (i.e., the first 0.75 kg of the distillate is removed), then the middle 15% to 95% of the distillate is collected (i.e., the middle 4 kg is collected and used as the purified organic solvent), and the last 5% of the distillate distilled from the still is not collected (i.e., the last 0.25 kg of the distillate is removed).

[0032] More specifically, the organic solvent preparation step may further include purging the organic solvent with nitrogen gas for 10 to 30 minutes before distilling the organic solvent in a distiller to remove trace impurities contained in the organic solvent and reduce the influence of trace impurities on the analysis of residual acid, and then distilling the organic solvent in an atmosphere filled with nitrogen gas. Here, the distillation temperature for the organic solvent in the distiller is preferably 75°C to 80°C, and the gas pressure is preferably normal pressure.

[0033] In the organic solvent preparation step, the method for purging the organic solvent with nitrogen gas is not particularly limited, but for example, the organic solvent can be forcibly purged with nitrogen gas by inserting a nitrogen gas pipe below the liquid surface of the organic solvent.

[0034] In one embodiment of the present invention, the organic solvent may be, for example, a monohydric alcohol-based organic solvent, such as ethanol (also called absolute alcohol).

[0035] In the organic solvent preparation process, the first distillate (e.g., the first 10% to 15% of the distillate) distilled from the still contains low-boiling point compounds (e.g., trace amounts of aldehyde compounds). The last distillate (e.g., the last 5% to 10% of the distillate) distilled from the still contains high-boiling point compounds (e.g., trace amounts of acid compounds). In other words, the purified organic solvent, which is the intermediate portion collected in the organic solvent preparation process, does not contain the trace amounts of aldehyde compounds contained in the first distillate or the trace amounts of acid compounds contained in the last distillate, thereby preventing the aldehyde compounds and acid compounds from affecting the subsequent analysis of residual acids. Note that the purified organic solvent, which is the intermediate portion collected in the organic solvent preparation process, is used in the subsequent process.

[0036] In step S120, a titrant preparation step is carried out in which a basic inorganic compound and (at least a part of) the purified organic solvent obtained in step S110 are mixed to prepare a titrant.

[0037] In one embodiment of the present invention, the basic inorganic compound may be potassium hydroxide (e.g., reagent grade or analytical grade potassium hydroxide). The equivalent concentration of the basic inorganic compound in the titrant is 0.005 N or less, preferably 0.0001 N to 0.005 N, and particularly preferably 0.0005 N to 0.005 N. For example, the equivalent concentration of the basic inorganic compound in the titrant may be 0.00075 N, 0.001 N, 0.002 N, 0.003 N, 0.004 N, or 0.005 N.

[0038] By ensuring that the equivalent concentration of the titrant obtained in step S120 is within the above range, the detection limit of the acid value analysis in the subsequent titration step can be improved, and for example, the detection accuracy of the residual acid analysis can reach a concentration level of 0.0001 mg KOH / g. On the other hand, if the equivalent concentration of the basic inorganic compound in the titrant exceeds 0.005 N, the detection accuracy of the residual acid analysis cannot reach a concentration level of 0.0001 mg KOH / g.

[0039] In one embodiment of the present invention, the step of preparing a titrant may further include adding a 0.05 to 2 N hydrochloric acid standard solution (preferably, a 0.1 N hydrochloric acid standard solution (purchased from Sigma-Aldrich)) to the ethanol solution. By adding a 0.05 to 2 N hydrochloric acid standard solution, the equivalent concentration can be confirmed.

[0040] In step S130, a test sample preparation step is carried out in which a diol compound to be measured and (at least a part of) the purified organic solvent obtained in step S110 are mixed to prepare a liquid test sample, in which the amount of residual acid in the diol compound to be measured is unknown.

[0041] The weight ratio of the diol compound to the organic solvent in the test sample (diol compound:organic solvent (weight ratio)) is preferably 1:1 to 1:4, and more preferably 1:1 to 1:2.

[0042] For example, in the test sample preparation step, the test sample may be prepared by mixing 1 kg of a diol compound with 2 kg of a purified organic solvent, but the present invention is not limited thereto.

[0043] Here, the diol compound may be an aromatic dihydroxy compound, for example, bisphenol A (BPA).

[0044] In one embodiment of the present invention, in the step of preparing a test sample, a diol compound and a purified organic solvent may be placed in a container (e.g., a three-neck flask) and mixed in an atmosphere filled with nitrogen gas. Regarding the order of addition of the materials, for example, the diol compound may be added first, and then the purified organic solvent may be added in an atmosphere filled with nitrogen gas to prepare the test sample. The liquid temperature during mixing may be maintained at, for example, 20°C to 25°C, but the present invention is not limited thereto.

[0045] In one embodiment of the present invention, the test sample preparation step may further include purging the mixture of the diol compound to be measured and the purified organic solvent with nitrogen gas. Purging the mixture with nitrogen gas removes impurities contained in the diol compound and reduces the influence of the impurities on the residual acid analysis. The nitrogen gas purging is carried out for a predetermined time, for example, 10 to 30 minutes.

[0046] In the process of preparing the test sample, the method of purging the mixture with nitrogen gas is not particularly limited, but for example, the mixture can be forcibly purged with nitrogen gas by inserting a nitrogen gas pipe below the liquid surface of the mixture.

[0047] The purified organic solvent obtained in step S110 is preferably used within 24 hours (i.e., mixed with a basic inorganic compound to prepare a titrant in step S120 and / or mixed with a diol compound to prepare a test sample in step S130). Using the purified organic solvent within 24 hours can prevent the purified organic solvent from reacting with carbon dioxide in the air to produce other impurities that could affect detection accuracy.

[0048] In step S140, the test sample obtained in step S130 is subjected to acid-base titration using the titrant obtained in step S120, and when the titration endpoint is reached, the acid value of the diol compound (i.e., the amount of residual acid in the diol compound) is calculated. In addition, the acid-base titration can be performed, for example, by potentiometric titration.

[0049] The detection accuracy of the residual acid analysis by the method for analyzing residual acids of alcohol compounds according to the embodiment of the present invention can reach a concentration level of 0.0001 mg KOH / g.

[0050] The method for analyzing the residual acid of an alcohol compound of the present invention can accurately quantify the residual acid of a diol compound (e.g., bisphenol A (BPA)), and can provide acid number information with an accuracy of 0.0001 mg KOH / g, for example, when the diol compound is shipped to a downstream production unit or a customer. [Example]

[0051] [Experimental data and measurement results] In order to demonstrate the technical effect of the method for analyzing residual acid of alcohol compounds according to the present invention, the present invention will be further illustrated in detail below with experimental data and results, but the scope of protection of the present invention is not limited to these examples.

[0052] Example 1 [Organic solvent preparation process] Five kg of absolute alcohol (ethanol) was supplied to a still and distilled under a nitrogen gas atmosphere. The first 15% (0.75 kg) of the distillate was not collected, but the subsequent 15 to 95% (4 kg) of the distillate was collected and prepared as purified absolute alcohol. The final 5% (0.25 kg) of the distillate was also not collected. [Titration solution preparation process] Potassium hydroxide (KOH) and a portion of purified absolute alcohol were mixed to prepare a titrant with a KOH concentration of 0.005 N. The concentration of the prepared KOH titrant was confirmed with 0.1 N HCl (Sigma-Aldrich hydrochloric acid standard solution prepared in ethanol). [Test sample preparation process] A 1 kg sample of bisphenol A (BPA) with an unknown amount of residual acid was weighed and placed in a three-neck flask. Under a nitrogen gas atmosphere, 2 kg of purified absolute alcohol was added and stirred until uniform. A nitrogen gas tube was then inserted below the liquid surface and purged for 15 minutes to prepare the test sample. The liquid temperature was maintained between 20°C and 25°C. [Titration process] The titrant was used to perform potentiometric titration on 100 g of the sample to be tested for BPA, and acid value analysis was performed. The results are shown in Table 1. The titration was performed using an automatic potentiometric titrator manufactured by Kyoto Electronics Manufacturing Co., Ltd. (KEM). The unit of acid value is 10E. -3 The acid value was calculated as mgKOH / g. The acid value was calculated using the following formula:

[0053] Acid number = (amount of KOH consumed (cc) × f × 56.1) / liquid weight of test sample. Here, the KOH consumption (cc) is the volume (cc) of KOH used in the titration after adding the sample, and the volume (cm) of the alkaline solution (potassium hydroxide, KOH) consumed during the titration process. 3 or cc). f is the defined equivalence factor of KOH. 56.1 is the molar mass of potassium hydroxide (KOH) in milligrams, which is used to convert the amount of KOH consumed from volume to mass and calculate the number of milligrams of KOH required to neutralize the free fatty acids in the sample. The liquid weight of the test sample (g) is the mass (in g) of the test sample. The acid number is determined by calculating the percentage of the mass of potassium hydroxide (after adjusting for the equivalence factor) required under specific conditions to neutralize all the free fatty acids in the sample. The acid number is expressed in mgKOH / g and is a quantitative parameter that directly reflects the free fatty acid content of an oil or other substance.

[0054] <Examples 2 to 5, Comparative Examples 1 to 3> Acid value analysis was performed in the same manner as in Example 1, except that the KOH concentration in the titration solution and the liquid weight of the test sample (the concentration of each test sample was the same) were changed as shown in Table 1. The results are shown in Table 1.

[0055] [Table 1]

[0056] In Examples 1 to 4, in which the KOH concentration of the titrant used was 0.001N to 0.005N, the analyzed acid value was approximately 13.1205 to 15.6923*10E -3 mgKOH / g, showing stable acid value measurement results at a sufficiently low concentration level.

[0057] In Examples 2 to 4, where a titrant with a KOH concentration of 0.001 N was used, acid value analysis was performed using different liquid weights (50 to 100 g) of the BPA test sample, but essentially the same results (acid value) were obtained. In Example 5, where a titrant with a KOH concentration of 0.0001 N was used, the acid value measurement result was slightly higher, but within the acceptable range for the analysis result.

[0058] In Examples 1 to 5, distilled purified absolute alcohol was used to prepare the titrant and test sample, and the acid value of the BPA test sample was analyzed by using a titrant with a KOH concentration of 0.0001N to 0.005N.

[0059] In Comparative Examples 1 to 3, in which a titrant with a KOH concentration of 0.01 N was used, the endpoint of the titration could not be determined because the KOH concentration of the titrant was too high. In other words, if a titrant with a KOH concentration exceeding 0.005 N is used, it may not be possible to analyze the acid value.

[0060] <Comparative Example 4> In Comparative Example 4, anhydrous alcohol (ethanol) was used as the solvent without distillation (purification), and the acid value analysis was carried out in the same manner as in Experimental Example 1. As a result, the titration endpoint could not be determined, and the acid value could not be analyzed.

[0061] [Advantageous Effects of the Embodiments] The analytical method for residual acids of alcohol compounds according to the present invention includes the following technical features: "a step of preparing an organic solvent, introducing the organic solvent into a distiller to distill the organic solvent, removing at least the first 10% of the distillate distilled from the distiller, and collecting an intermediate portion of the distillate distilled from the distiller to obtain a purified organic solvent," "a step of preparing a titration solution by mixing a basic inorganic compound with at least a portion of the purified organic solvent," "a step of preparing a test sample by mixing a diol compound to be measured with at least a portion of the remaining purified organic solvent," and "a titration step of performing acid-base titration on the test sample with the titration solution to analyze the amount of residual acids of the diol compound." These technical features enable improved detection accuracy of residual acids of alcohol compounds, thereby enabling detection of residual acids of alcohol compounds at sufficiently low concentration levels and improving the detection limit.

[0062] The above disclosure is a preferred embodiment of the present invention, and the scope of the claims of the present invention is not limited thereto. All equivalent technical modifications made by utilizing the contents of the specification and drawings of the present invention are included in the scope of the claims of the present invention. [Explanation of symbols]

[0063] S110...Process S110 S120...Process S120 S130...Process S130 S140...Process S140

Claims

1. preparing an organic solvent, including providing an organic solvent, placing the organic solvent in a still to distill the organic solvent, removing at least a first 10% of the distillate distilled from the still, and collecting an intermediate portion of the distillate distilled from the still to obtain a purified organic solvent; a titration solution preparation step of mixing a basic inorganic compound with at least a portion of the purified organic solvent to prepare a titration solution having an equivalent concentration of the basic inorganic compound of 0.005 N or less; a test sample preparation step of mixing a diol compound to be measured with at least a portion of the remaining portion of the purified organic solvent to prepare a test sample; a titration step of performing acid-base titration on the test sample with the titrant to analyze the amount of residual acid in the diol compound; A method for analyzing residual acids in alcohol compounds, comprising:

2. 2. The method for analyzing residual acids in alcohol compounds according to claim 1, wherein the organic solvent is ethanol, the basic inorganic compound is potassium hydroxide, and the diol compound is an aromatic dihydroxy compound.

3. 2. The method for analyzing residual acids of alcohol compounds according to claim 1, wherein in the step of preparing the organic solvent, at least the first 10% to 15% of the distillate distilled from the still is removed, and then the middle portion of the distillate distilled from the still is collected from 10% to 15% to 90% to 95% to obtain the purified organic solvent, and the last 5% to 10% of the distillate distilled from the still is removed.

4. 4. The method for analyzing residual acids of alcohol compounds according to claim 3, wherein the first distillate distilled from the still contains low-boiling aldehyde compounds, and the last distillate distilled from the still contains high-boiling acid compounds.

5. 2. The method for analyzing residual acids of alcohol compounds according to claim 1, wherein the step of preparing the organic solvent further comprises purging the organic solvent with nitrogen gas for 10 to 30 minutes before distilling the organic solvent in the distiller, and then distilling the organic solvent in the distiller filled with the nitrogen gas.

6. 2. The method for analyzing residual acids of alcohol compounds according to claim 1, wherein the equivalent concentration of the basic inorganic compound in the titrant is 0.0001N to 0.005N.

7. 7. The method for analyzing residual acids of alcohol compounds according to claim 6, wherein the equivalent concentration of the basic inorganic compound in the titrant is 0.0005N to 0.005N.

8. 2. The method for analyzing residual acids of alcohol compounds according to claim 1, wherein a weight ratio of the diol compound to the organic solvent in the test sample (the diol compound:the organic solvent (weight ratio) in the test sample) is 1:1 to 1:

4.

9. 2. The method for analyzing residual acids of alcohol compounds according to claim 1, wherein the test sample preparation step further comprises purging a mixture of the diol compound to be measured and at least a portion of the remainder of the purified organic solvent with nitrogen gas.

10. 2. The method for analyzing residual acid in alcohol compounds according to claim 1, wherein the titration step is performed by acid-base titration using potentiometric titration.

Images